Michael Smith, professor at the University of Missouri, told ARSBC participants that protocols assuring high pregnancy rates require two key components of successful estrus detection and high conception rates. Any small drop in either of those factors, and the pregnancy rate on a herd will suffer.

“The good things you do in your management don’t compensate for the mistakes that occur,” Smith said, “but rather those mistakes that occur cancel out the good things you’re doing in regard to reproduction.”

Highly successful operations, Smith said, typically target a 67 percent pregnancy rate (estrus detection rate as a factor of conception rate). Careful preparation and management yields key advantages for producers, “when you get a large portion of your females pregnant the first day of the breeding season.”

Smith outlined key decisions to answer before the breeding season on whether to implement A.I.:

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  • With heifers, determine if the pregnancy rate has been more 85 percent in recent years, over a 60- to 70-day period of time. If yes, then your heifers are good candidates for a synchro program. If less, “there may be other management considerations to put into place before synchro program,” Smith said.
  • Eliminate heifers that have received growth-promoting implants within 30 days after birth. Those implants impair uterine development and reduce preg rates.
  • Select an appropriate target weight for heifers to hit by the start of breeding. Smith said the usual recommendation is 60 to 65 percent, but new data suggest it could be lower.
  • What is the heifer’s reproductive tract score? The RTS, a subjective measure for where the heifer is in puberty, ranges from 1 to 5 and is determined through palpation of uterus and ovaries. Heifers ranging from 4 to 5 are cycling as they should. Smith recommends “that 50 percent of heifers have a 4 or 5 around four to six weeks before breeding season.
  • Body Condition Score (BCS) at calving  and as you approach synchronization.
  • Have your total cows’ average to be at 40 to 50 days postpartum when synchro begins.
  • Purchase semen from major A.I. companies. Custom collection from individual sires may be successful, Smith said, but semen from the four major companies results in an average pregnancy rate of 61 percent. Those sires are used repeatedly and have proven stamina and accuracy within their EPDs. end mark

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Michael Smith of the University of Missouri speaks to participants at the Applied Reproductive Strategies in Beef Cattle convention. Staff photo.